The present invention relates to thermal control systems generally, and more specifically to flow control structures for air cooled devices.
Thermal control systems are necessary to prevent overheating of computer processors. Most processors in modern desktop computers require a heat sink with forced air convection. For example, a conventional heat sink for a xe2x80x9cPENTIUM 4xe2x80x9d processor has a flat, solid base plate to which a plurality of fins are affixed. A small fan is placed on top of the fin stack, such that a flow of air is directed downward through the fin structure towards the flat plate. The bottom of the flat plate is placed on the heat source to be cooled, i.e., the computer CPU. The air flow impinges on the base plate inside the fin structure and splits into two flows which exit on two opposing sides of the heat sink.
The most common fans used for this purpose are of the axial type, including a central hub, through which air does not flow. This creates an air flow having an outer region with a relatively high air velocity, and an inner region with a relatively low (or zero) air velocity. Thus, there is a relatively large region directly along the axis of the fan, in which the air moves slowly. The slow moving air creates a region of poor heat transfer. With little air impinging on the central region, heat must be conducted laterally through the heat sink to the outer region, where the air flow and heat removal are greater. Unfortunately, the fan is typically located right over the heat source (i.e., the CPU), so that the region of poorest heat transfer is located right above the heat source.
U.S. Pat. No. 5,615,084 describes a parallel plate heat sink used in conjunction with an air moving device which provides an annular flow of air against the heat sink. A flow deflector selectively blocks potential exhaust paths so as to redirect some of the flow of air through the region under the central hub of the fan. This transforms some of the otherwise stagnant air volume in the center of the heat sink to more rapidly moving cooling air.
An improved cooling system is desired.
One aspect of the present invention is a cooling system, comprising a heat sink having a plurality of fins, a fan positioned near the heat sink to blow air between the fins, and flow converging means positioned between the fins and the fan, to cause air from the fan to converge on a predetermined region of the heat sink.
Another aspect of the invention is a cooling system, including a heat sink having a plurality of fins. A fan is positioned near the heat sink to blow air between the fins. A flow converging device is provided from the group consisting of a plurality of wedges and a body having a frustum shaped opening therethrough. The flow converging device is positioned between the fins and the fan, to cause air from the fan to converge on a predetermined region of the heat sink.
Another aspect of the invention is a method for cooling a device, comprising the steps of: generating an air flow having an outer region with a first flow velocity and an inner region with a second flow velocity less than the first flow velocity; directing the air flow through a converging device, so the air flow from the outer region is converged into the inner region; and directing the converged air flow between a plurality of fins on a predetermined region of a heat sink.